disk warning added

Author: manishmsfte

articles/managed-instance-apache-cassandra/create-cluster-cli.md

@@ -86,7 +86,7 @@ This quickstart demonstrates how to use the Azure CLI commands to create a clust
 1. Create a datacenter for the cluster with three virtual machines (VMs). Use the following configuration:
 
    - **VM size**: Standard E8s v5
-   - **Data disks**: 4 P30 disks attached to each of the VMs deployed
+   - **Data disks**: 4 P30 disks attached to each of the VMs deployed, When calculating storage capacity, assume a maximum sustained usage of 50%. This buffer accounts for tombstones and disk consumption by system services. Additionally, backups temporarily consume disk space before data is persisted to Blob storage.
 
    After all the information is in place, use the [az managed-cassandra datacenter create](/cli/azure/managed-cassandra/datacenter#az-managed-cassandra-datacenter-create) command:
 

articles/managed-instance-apache-cassandra/create-cluster-portal.md

@@ -79,7 +79,7 @@ If you don't have an Azure subscription, create a [free account](https://azure.m
    We introduced write-through caching (public preview) by using L-series VM product tiers. This implementation aims to minimize tail latencies and enhance read performance, particularly for read-intensive workloads. These specific product tiers are equipped with locally attached disks, which ensure increased IOPS for read operations and reduced tail latency.
 
    Write-through caching is provided without a service-level agreement (SLA). We don't recommend it for production workloads. For more information, see [Supplemental Terms of Use for Microsoft Azure Previews](https://azure.microsoft.com/support/legal/preview-supplemental-terms/).
-   - **No. of disks**: Choose the number of p30 disks to be attached to each Cassandra node.
+   - **No. of disks**: Choose the number of p30 disks to be attached to each Cassandra node. When calculating storage capacity, assume a maximum sustained usage of 50%. This buffer accounts for tombstones and disk consumption by system services. Additionally, backups temporarily consume disk space before data is persisted to Blob storage.
    - **No. of nodes**: Choose the number of Cassandra nodes to deploy to this datacenter.
 
       :::image type="content" source="media/create-cluster-portal/create-datacenter-page.png" border="true" alt-text="Screenshot that shows the Data center tab where you can review the values." lightbox="media/create-cluster-portal/create-datacenter-page.png":::
@@ -146,7 +146,7 @@ Scaling is an online operation and works in the same manner as described for pat
    * **Availability zone**: Select if you want to enable availability zones in this datacenter.
    * **Location**: Location where your datacenter is deployed.
    * **SKU size**: Choose from the available VM product tier sizes.
-   * **No. of disks**: Choose the number of p30 disks to be attached to each Cassandra node.
+   * **No. of disks**: Choose the number of p30 disks to be attached to each Cassandra node. When calculating storage capacity, assume a maximum sustained usage of 50%. This buffer accounts for tombstones and disk consumption by system services. Additionally, backups temporarily consume disk space before data is persisted to Blob storage.
    * **No. of nodes**: Choose the number of Cassandra nodes to deploy to this datacenter.
    * **Virtual network**: Select an existing virtual network and subnet.